1. Field of the Invention
The present invention relates to circuit modules, and more specifically to a circuit module including an electronic component mounted thereon.
2. Description of the Related Art
Known circuit modules include a 2-port nonreciprocal circuit device (hereinafter simply called a nonreciprocal circuit device) described in, for example, Japanese Unexamined Patent Application Publication No. 2009-49879. Hereinafter, the nonreciprocal circuit device described in Japanese Unexamined Patent Application Publication No. 2009-49879 is described with reference to the attached drawings. FIG. 6 is an exploded perspective view of a nonreciprocal circuit device 500. In FIG. 6, the direction of the line normal to the main surface of a circuit substrate 510 is defined as a z-axis direction. When an electronic component 502 is viewed in plan view from the z-axis direction, a direction that extends along the long side of the electronic component 502 is defined as an x-axis direction, and a direction that extends along the short side of the electronic component 502 is defined as a y-axis direction.
The nonreciprocal circuit device 500 includes the electronic component 502 and the circuit substrate 510. The nonreciprocal circuit device 500 includes a substantially plate-shaped yoke in addition to the electronic component 502 and the circuit substrate 510, but the substantially plate-shaped yoke and the like are omitted in FIG. 6.
The electronic component 502 includes a component body 503 and external electrodes 504, 506, and 508. The component body 503 has a substantially rectangular parallelepiped shape, and contains two coils. The external electrodes 504, 506, and 508 are arranged in a row along the x-axis direction on a lower (in the negative direction of the z-axis) main surface (hereinafter called a mounting surface S1) of the component body 503 at the center of the mounting surface S1 in the y-axis direction.
The circuit substrate 510 includes a substrate body 512 and external electrodes 514, 516 and 518. The substrate body 512, which is a substantially plate-shaped substrate, contains a capacitor, a resistor, and the like. The external electrodes 514, 516 and 518 are arranged in a row along the x-axis direction on an upper (in the positive direction of the z-axis) main surface (hereinafter called a main surface S2) of the component body 503. The external electrodes 504, 506, and 508 are respectively connected to the external electrodes 514, 516 and 518. As a result, the electronic component 502 is mounted on the circuit substrate 510, and the nonreciprocal circuit device 500 is formed. The nonreciprocal circuit device 500 described above has a characteristic in that a signal is allowed to be transmitted only in a predetermined direction, and not in the opposite direction.
However, in the nonreciprocal circuit device 500 described in Japanese Unexamined Patent Application Publication No. 2009-49879, it is difficult to mount the electronic component 502 on the circuit substrate 510 reliably, as described below. FIG. 7 is an illustration of the nonreciprocal circuit device 500 viewed in plan view from the positive direction of the x-axis.
As described above, the external electrodes 504, 506, and 508 are arranged in a row along the x-axis direction on the mounting surface S1 of the component body 503, which is located on the negative direction side in the z-axis direction, at the center of the mounting surface S1 in the y-axis direction. Hence, in the nonreciprocal circuit device 500, the electronic component 502 is fixed to the circuit substrate 510 only at the center thereof in the y-axis direction, as illustrated in FIG. 7. In other words, the electronic component 502 is not fixed to the circuit substrate 510 at the both ends thereof in the y-axis direction. Hence, due to an external shock, for example, the electronic component 502 may possibly fall over onto the circuit substrate 510 in the directions denoted by the arrows in FIG. 7. As a result, wiring lines between the electronic component 502 and the circuit substrate 510 may possibly be broken.